Arya Stark, the night wolf, daughter of the North.
Aryas journey away from the rest of her family has been one of putting on new faces and names. Even as soon as she escaped the red keep, she accepted the label of urchin almost immediately. However, she never really shed her previous identity, just adding a new layer of paint on top. It wasn't until the House of Black and White that she stripped away Salty, Lumpyhead, and Weasle, but try as she might, she can't scrape away Arya Stark.
Even after being blinded, and on the streets. Forced to let got. Even after she believes she is nobody. As soon as someone from her list arrives, Arya Stark peaks through.
I think returning Arya to Westeros is one of the corners Martin has written himself into, and I cannot say that I know how to fix that. I can however talk about some things I want to happen.
The first thing I'll note is something present in the visuals here. I depicted Arya with Little Finger's Dagger, and a Valyrian Steel rapier. I want house Stark to get the two parts of ice back, but instead of reforging it into blade, for Widows Wail to be worked into a sword for Arya. Maybe call it Icicle.
I'd also like her and Gendry to meet again. I don't necesarrily want this to be romantic, because Arya is only about 11 years old, but they have a very fun friendship. I think this could also help Arya meet with Lady Stone Heart, and return some semblance of sanity for her mother.
I think in part, Arya's story won't end with A Song of Ice and Fire, because she is so young. If she is to receive a happy "ending" it would be a reunion with her family back at Winterfell.